Calcium is the most prevalent mineral in the human body. About 99% of the body's calcium resides in the bones and teeth, and the remaining 1% is found in other body fluids and cells.

Functions

Calcium's functions include:

Builds bones, both in length and strength

Helps bones remain strong by slowing the rate of bone loss with age

Helps muscles contract

Helps the heart beat

Plays a role in normal nerve function, transfers nerve impulses

Helps blood clot during bleeding

Builds healthy teeth (in kids)

Recommended Intake

The Institute of Medicine offers these recommendations:

Age Group
(in years)

Recommended Dietary Allowance or •Adequate Intake (mg/day)

Females

Males

Birth to 6 months

200 milligrams (mg)

200 mg

7-12 months

260 mg

260 mg

1-3 years

700 mg

700 mg

4-8 years

1,000 mg

1,000 mg

9-18 years

1,300 mg

1,300 mg

19-50 years

1,000 mg

1,000 mg

51-70 years

1,200 mg

1, 000 mg

71 years and older

1,200 mg

1,200 mg

Pregnant or lactating teens

1,300 mg

n/a

Pregnant or lactating adults

1,000 mg

n/a

Calcium Deficiency

In childhood, not getting enough calcium may interfere with growth. A severe deficiency may keep children from reaching their potential adult height. Even a mild deficiency over a lifetime can affect bone density and bone loss, which increases the risk for osteoporosis as an adult.

If you do not consume enough calcium, your body will draw from the storage in your bones in order to supply enough calcium for its other functions: nerve transmission, muscle contraction, heartbeat, and blood clotting.

Calcium Toxicity

Very large doses over a prolonged period of time may cause kidney stones and poor kidney function. Your body may not absorb other minerals, such as
iron,
magnesium, and
zinc, properly. These problems could occur from consuming too much through a calcium supplement, not from milk or other calcium-rich foods. The tolerable upper intake level (UL) depends on age.

Age Group
(in years)

Upper Level Intake (mg/day)

Females

Males

Birth to 6 months

1,000 milligrams (mg)

1,000 mg

7-12 months

1,500 mg

1,500 mg

1-8 years

2,500 mg

2,500 mg

9-18 years

3,000 mg

3,000 mg

19-50 years

2,500 mg

2,500 mg

51 years and older

2,000 mg

2,000 mg

Pregnant or lactating teens

3,000 mg

n/a

Pregnant or lactating adults

2,500 mg

n/a

Major Food Sources

Dairy foods—milk, yogurt, and some cheeses—are the best dietary sources of calcium. These foods are also rich in vitamin D, which helps the body absorb calcium.

Food

Serving size

Calcium content
(mg)

Yogurt, plain, low fat

1 cup

415

Milk, nonfat

1 cup

299

Cheddar cheese

1.5 ounces

307

Mozzarella cheese, part skim

1.5 ounces

333

Cottage cheese, 1% milkfat

1 cup

138

Frozen yogurt, soft serve

½ cup

103

Ice cream

½ cup

84

Sardines, canned in oil with bones

3 ounces

313-384

Salmon, pink, canned solids with bone

3 ounces

181

Bread, white

1 slice

73

Pudding, chocolate, ready to eat

4 ounces

55

Orange juice, calcium-fortified

6 ounces

261

Soymilk, calcium-fortified

8 ounces

299

Absorption of calcium from some other dietary sources is not as great as that from dairy foods. Specifically, dark green vegetables contain oxalates, and grains contain phytates, which can bind with calcium and decrease their absorption.

Read food labels to determine the specific calcium levels of these foods.

Health Implications

Bone Health and Osteoporosis Prevention

Calcium is essential to build and maintain strong bones at all stages of life. Bone growth begins at conception, and bones grow longer and wider until well into the 20s. After this type of growth is complete, bones gain in strength and density as they continue to build up to peak bone mass by about age 30. From this point on, as a natural part of the aging process, bones slowly lose mass. Calcium is essential to slow this natural loss and stave off the onset of osteoporosis—a disease in which bones become fragile and more likely to break.

Tips for Increasing Your Calcium Intake

Make your own salad dressing by combining low-fat plain yogurt with herbs.

Add tofu (processed with calcium) to soups and pasta sauce.

If you like fish, eat canned fish with bones on crackers or bread.

For dessert, try low-fat frozen yogurt, ice cream, or pudding.

In baked goods, replace half of the fat with plain yogurt.

Taking Supplements

If you are unable to meet your calcium needs through dietary sources, consider a calcium supplement. Some points to remember when choosing and using a calcium supplement include:

Check the label because the amount of calcium differs among products.

Avoid supplements with dolomite or bone meal. They may contain lead.

Check your vitamin D intake, too. This vitamin is essential for absorption of calcium. Milk is a great source of vitamin D, as is sunlight.

If you take both calcium and iron supplements or a multivitamin with iron, take them at different times of the day. They can impair each other's absorption. This is also true of chromium, manganese, magnesium, and zinc.

Do not take more than 500 mg of calcium at a time. Taking the calcium with food can help absorption.

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